1. Field of the Invention
The present invention relates to an image pickup apparatus for picking up an image of an object.
2. Related Background Art
Japanese Patent Application Laid-Open No. 2000-201355 A discloses a method of reading out charges of all pixels by performing partial readout for three times using an interline type solid state image pickup element, that is, a reading out method in which one frame is constituted by three fields.
Moreover, it is also disclosed that an image pickup apparatus using the reading out method includes switching means for switching between an all pixel mode for reading out charges of all pixels in three fields and a monitoring mode for repeating read-out of one field among the three fields.
However, the conventional example has a problem in that charges of pixels of fields other than a field to be outputted are not effectively utilized in the monitoring mode. Further, there is a problem in that, since a solid state image pickup element used in an electronic still camera tends to have higher number of pixels under present circumstances, a thinning-out ratio of 1/3 is insufficient.